Kamon is Japanese traditional symbol to identify an individual, family.
Kamon is written 家紋 in chinese character. 家[ka] means “family” and 紋[mon] means “symbol”, “mark”.
The origin of Kamon was in Heian period (794-1185).
People had drawn many patterns on equipments since Nara period (710-794), but they were just for decorations. Then, Kuge (aristocratic class) started to use them on bullock carts to identify the carts.
Heiji monogatari emaki (The tale of Heiji)
On the other hand, Buke (military house) started to use Kamon in the end of Heian period to distinguish among friends and enemies in the battle.
Sekigahara no Kassen Byōbu-zu (Gifu History Museum)
Famous Kamon of Feudal Samurai Warlords (Shogun)
Source: Encyclopedia JAPAN
In the Edo period (1603-1868), since there were few hard battles among samurai, the role of Kamon was changed to be a kind of symbol of authority.
At that time, Japan was a hierarchical society of samurai, farmers, artisans, and merchants（士農工商=4 occupations), so that Kamon was used to indicate social status.
But unlike in Europe where only aristocrats were allowed to use emblems, everyone could use Kamon in Japan.
Kabuki actor wearing a costume with his Kamon
And in this period, it became normal using Kamon on formal dress such as Hakama or Kamishimo
Kamishimo is full dress for men. You can see Kamon on chest and back.
Still today, Montsuki-Hakama (Hakama with Kamon) is the standard of formal dress.
Yuzuru Hanyu, the gold medalist of figure ice skating in 2014 and 2018 Winter Olympics, was wearing Montsuki-Hakama when he was honored by the government of Japan.
And also, many Kamon is still working.
Kamon of Japanese emperor “Kiku-mon” (kiku=chrysanthemum) are printed.
Many big and historical companies have logos from the Kamons of their founders.
Mitsui & Co.
by Kashiwa Sato
“Mitsui” is written “三井” in chinese character.
And in these days, you can see many logos inspired by Kamon in Japanese graphic design.
COREDO Muromachi logos
by Shoryu Hatoba, a Kamon designer
Tokyo Olympic and Paralympic games logo
by Asao Tokoro , an enthusiast of Kamon
And I’m also impressed by kamon.
You can see the relevance to it in some of my works
Takasago seika, 2016
You can know about kamon well through the sites below.